Polysiloxane-containing copolymers were synthesized and characterized by nuclear magnetic resonance and elemental analysis. These copolymers were neutralized by triethylamine. The copolymers could be self-emulsified to form emulsions in water with and without cosolvent PCS and exhibited excellent defoaming abilities. These copolymers were also used as emulsifiers to emulsify silicone oil in water to form stable oil-in-water emulsions. This emulsion again exhibited defoaming properties, more efficiently than that of the self-emulsified emulsion of siliconized acrylic copolymer (SAA).